1. Field of the Invention
The present invention relates to a turbine fuel pump preferably used, for example, for supplying fuel to an injection valve and the like of an engine installed on a vehicle.
2. Description of the Related Art
In general, for supplying fuel to an engine, an electronically controlled fuel injection device is installed on a vehicle (passenger car) and the like. The fuel injection device is constituted of an injection valve, a fuel pump and the like. The injection valve is for injecting fuel to a combustion chamber of the engine, while a fuel pump is for discharging the fuel (in a fuel tank installed on a rear side of the vehicle) to the injection valve.
Japanese Patent Unexamined Publication No. showa 60 (1985)-47894 (=JP60047894) equivalent of U.S. Pat. No. 4,938,659 discloses a turbine fuel pump (entitled xe2x80x9cFUEL PUMPxe2x80x9d in U.S. Pat. No. 4,938,659). The turbine fuel pump in U.S. Pat. No. 4,938,659 includes a casing, an upper cover, a pump housing, and an impeller. The casing is shaped substantially into a barrel and cases therein an electric motor. The upper cover is disposed on a first side of the casing. The pump housing is disposed at a second end of the casing in such manner as to support the electric motor between the upper cover and the pump housing. Moreover, the pump housing has an annular fuel passage between an intake port and a delivery port for respectively taking in and delivering the fuel. The impeller is housed in the pump housing and is rotated by the electric motor.
It is an object of the present invention to provide a turbine fuel pump.
It is another object of the present invention to improve pump efficiency of the turbine fuel pump by designing profile of a flow path in view of profile length and the like of the flow path.
According to a first aspect of the present invention, there is provided a turbine fuel pump, comprising:
i) a casing for casing therein an electric motor;
ii) a pump housing disposed at the casing, the pump housing being formed with an intake port and a delivery port for respectively taking in and delivering fuel, the pump housing including a fuel passage between the intake port and the delivery port, the fuel passage including a flow path defining a cross section S; and
iii) an impeller rotatably disposed in the pump housing, the impeller having an outer periphery formed with a vane which force feeds the fuel in the fuel passage of the pump housing when the impeller is rotated with the electric motor, the impeller being surrounded by the flow path, the vane of the impeller defining a height H and a thickness T.
The fuel passage defines the following typical dimension Rm, with respect to the cross section S of the flow path relative to the height 14 of the vane and the thickness T of the vane:
Rm=S/(2H+T). 
A wall of the flow path defining the cross section S is profiled by a profile length Lp, the profile length Lp divided by the typical dimension Rm making a dimension ratio Lp/Rm in a first range from 11 to 16.
According to a second aspect of the present invention, there is provided a pump housing, comprising:
i) a fuel passage formed between an intake port and a delivery port for respectively taking in and delivering fuel, the fuel passage including a flow path defining a cross section S; and
ii) an impeller rotatably disposed in the pump housing, the impeller having an outer periphery formed with a vane which force feeds the fuel in the fuel passage of the pump housing when the impeller is rotated with an electric motor, the impeller being surrounded by the flow path, the vane of the impeller defining a height H and a thickness T.
The fuel passage defines the following typical dimension Rm, with respect to the cross section S of the flow path relative to the height H of the vane and the thickness T of the vane:
Rm=S/(2H+T). 
A wall of the flow path defining the cross section S is profiled by a profile length Lp, the profile length Lp divided by the typical dimension Rm making a dimension ratio Lp/Rm in a first range from 11 to 16.
The other objects and features of the present invention will become understood from the following description with reference to the accompanying drawings.